Acoustical tile



March 7, 1967 5. PODGURSKI ACOUSTICAL TILE Original Filed Feb 1 1961 2 Sheets-Sheet 1 INVENTOR.

JOHN S. Ponciumsm BYVJW Ma ch'l. u-lQQFI g sdeqncsuasm 3,307,651

' MOU TIQ L E Original Filed Feb. 10, 1961 v 2 SheetsSheet 2 V o. v

IN V EN TOR.

JOHN S. Pooauasm "BY? 4 United States Patent 3,307,651 ACOUSTICAL TILE John S. Podgurski, Gypsum, Ohio, assignor to United States Gypsum Company, Chicago, 11]., a corporation of Delaware Original application Feb. 10, 1961, Ser. No. 88,340, now Patent No. 3,246,063, dated Apr. 12, 1966. Divided and this application Feb. 25, 1966, Ser. No. 530,116 4 Claims. (Cl. 181-63) This is a division of my copending application Serial No. 88,340, filed February 10, 1961, now Patent No. 3,246,063 issued April 12, 1966.

This invention relates to acoustical tile normally utilized in ceiling construction. More particularly, this invention relates to improved acoustical tile with an impervious backing.

A popular type of acoustical tile is made following generally the procedure set forth in United States Patent No. 1,769,519. According to the teachings of this patent, a mixture of granulated mineral wool, fillers, certain coloring materials, if needed, and a binder, particularly one of an amylaceous nature, such as thick boiling starch, is prepared for forming the body of the tile. This mixture or composition is placed upon suitable trays which have been previously covered with paper, such as newsprint, and then screeded to a suitable thickness with a reciprocatin'g edge. A pleasing surface, including elongated fissures, resembling that of travertine stone is normally obtained. Alternatively, by screeding in a different manner the surface can be made without the fissures. The trays are then placed in an oven, and dried or cured. The dried sheets, called slabs, are removed from the mold, dressed on both faces to provide smooth surfaces, to obtain the desired thickness and to prevent warping, and are then cut into tiles of a desired size.

Previous to this invention it had been assumed by those skilled in this art that for maximum drying speed the moisture should leave from both the bottom and the top surfaces of the drying slab and that covering the bottom surface with an impervious lamina would increase the drying time. Accordingly, the tray bottoms were made of foraminous material and covered with thin, relatively unsized layers of paper so as to facilitate the passage of water out of the back surface of the tile through the paper. Drying the composition under these conditions resulted in migration of the starch to both the bottom and top surfaces where it strengthened the surface areas. During the dressing operation, the face surface of the slab was normally sanded off to obtain a pleasing smooth surface, thereby removing a portion of the face area of high starch-concentration. The resulting tiles were found to warp unless the corresponding back surface area of high starch content was also sanded off. Thus, the back surface of the slabs was dressed by sanding oh the paper and a portion of the hardened composition to compensate for sanding of the other (face) side.

Removing the back surface of the slabs in the aforenoted process is not only a time-consuming and costly operation but also results in the loss of the paper and part of the cured composition, thereby necessitating the use and curing of extra material in initially forming the slabs.

Mineral fiber acoustical tiles, particularly the fissured type referred to above, are quite porous and thus readily transmit gases therethrough. Though high porosity is needed to give good sound absorption, a high degree of porosity presents a disadvantage when the tiles are used in certain ceiling constructions, particularly suspended acoustical ceilings with controlled ventilation systems, such for example as described in US. Patents Nos.

2,692,547, 2,781,557, 2,807,993, and 2,920,357. in such suspended ceilings the space immediately thereover serves as a plenum chamber for receiving and distributing air under pressure. This air then passes through the ceiling, at a controlled rate throughout the ceiling area, to the space below. When air passes through fissures or other random openings in the tile, the rate of flow is not only unpredictable but also uncontrollable, thus making it difficult or impossible to obtain a uniform flow pattern, such as has been found desirable in good air conditioning practice.

In addition, the porous nature of the mineral fiber acoustical tiles referred to above permits transmission of hot gases of combustion therethrough. This results in a markedly lowered fire rating for surfaces formed of such tiles, and is especially undesirable in suspended ceiling systems where a special effort is often necessary to attain a maximum resistance to fire transmission.

It is therefore an object of this invention to set forth an improvement in the manufacture of mineral fiber acoustical tiles formed by drying a porous composition spread upon trays.

It is another object of this invention to provide an improved acoustical tile, which has good acoustical characteristics, is impervious to the extraneous infiltration of gases therethrough and which is simple and economical to manufacture.

It is an added object of this invention to provide mineral fiber type acoustical tile for forming ceiling constructions which will facilitate control and uniform distribution of air from a plenum chamber formed in part from the ceiling construction.

Various other objects will readily occur to those skilled in the art to which this invention pertains from the following description.

In carrying out this invention in one form, a new and improved mineral fiber acoustical tile is produced by placing a metal foil sheet in the bottom of a slab-forming pan, depositing, screeding, drying and curing an amylaceous hinder-material fiber composition in the pan, removing the resulting slab, dressing only the face of the slab, and cutting the slab into tiles. The resulting tiles include a foil layer covering and bonded to their entire back face. An improved plenum chamber ceiling construction is formed by supporting a plurality of such tiles in edge to edge substantially co-planar relation to form a suspended ceiling comprising the lower wall of a plenum chamber. This construction is formed with controlled openings therethrough to provide controlled passage of gases through the ceiling to the space below.

For a more complete understanding of the invention, reference should be had to the drawings wherein:

FIG. 1 is a perspective view of a tile of the type forming the subject of this invention;

FIG. 2 is a schematic diagram of equipment for carrying out a process of manufacture of tiles as in FIG. 1;

FIG. 3 is a perspective View of 'a suspended ceiling construction utilizing tiles in accordance with the teachings of this invention; and

FIG. 4 is a perspective View of another suspended ceiling construction utilizing tiles in accordance with the teachings of this invention.

FIG. 1 illustrates a novel acoustical tile 10 including a baked mineral fiber composition body 12 and a layer of foil 14, such as aluminum foil (exaggerated in thickness in the drawings), firmly bonded to the back surface of the body. The tile 10 is provided with kerfs 16 for installation purposes, as will be later described.

' The structure of tile 10 and certain of the advantages of providing a tile of this construction are better illustrated and understood with reference to the novel process utes' and 'is then ready for use.

which the acoustical tile composition is to be spread and baked are lined with a sheet of foil 20 instead of with paper, as in the prior process outlined above. Analuminum foil of about .00035, or somewhat thicker, is preferred. The foil should be free from'any compound used during rolling which would adversely affect the bond between the foil and the mineralfiber composition. Foil sheet 20 is taken from the roll 22 and spread evenly as a continuous sheet over the line of molds or trays 18. The portion'of the foil sheet in each tray is then covered and the tray filled with -a plastic acoustical tile composition 24. Composition 24 is normally deposited in the trays, as the trays,'in abutting end to end relation, pass under feeder box 26 on a suitable conveyor, not shown. The feeder box is filled from the mixer 28 by the conveyor 30. The composition 24 is an amylaceous binder-mineral fiber composition, but can vary appreciably in content. A typical batch is made as follows: V

A starch binder is prepared from the following:

Thick boiling starch, pounds 300 Calcium sulfate hemihydrate, pounds 200 Water, gallons 595 The above is cooked at 180-195 F. for 5 to 8 min- Examples of presently available thick boiling starches are Corn Products Companys starch products 3123 and 3173 and A. E. Staley Manufacturing Companys starch product Sta-Thik.

135 gallons of the above starch binder are placed in a mixer and 250 lbs. of granulated mineral wool are mixed therewith fora total mixing time, for the entire formulation, of about 8-minutes to obtain an aqueous plastic'mix- After the composition 24 has been placed upon the trays they pass under the reciprocating screed bar 32, driven by the motor 34, which forms the fissures on the surface. A small rolly head 36 of the mix24 collects in back of the bar. The sheet of foil is then severed between succeeding trays, as bypassing a knife (not shown) between the trays,-and the filled trays pass into the oven 38 where their contents are dried and cured at a temperature between 250 and 300 F., for from 14 to 18 hours. The composition is thus dried and cured upon the foil, and the foil is thereby simultaneously bonded to the composition. After the composition has dried and cured in the oven 38 to form-slabs, thetrays reach the position 40, where the slabs 42 are removed from the trays. The foil is now slitters, also not shown, to form tiles'of the desired size.

The resulting tiles have metal foil covering the entire back surfaces and securely bonded to the body of the tiles by the amylaceous binder of the body.

During the drying of the slabs, the foil prevents any significant removal of moisture through the back surface and thus prevents any significant migration of starch toward this surface. The starch migrates only to the top surface of the slab. The improved starch migration pattern results in a greater concentration at the single sanding face where needed, or, if desired, permits a reduction in the amount of starch used. The resulting slab can be dressed by sanding the front face only, to obtain a desirable smooth surface and to trim the slab to the desired tile thickness, without encountering warping in the result- The use of metal foil as a back sheet provides a smooth even back surface and eliminates the need for sanding off the back surface of the slab or tile.

the cured composition or slabs from the trays and reinforces the back surface of the tiles.

The suspended ceiling construction illustrated in FIG.

3 serves as one wall of a plenum chamber for controlled ventilation of the spacebelow and incorporates tiles produced in accordance with this invention to particular advantage. In this type construction the air is uniformly distributed, through openings properly spaced throughout the ceiling area, into the room below. The openingsmay be formed .either in the tile, as shown in US. Patent No. 2,807,993, or inported hollow runners used to support adjacent rows of tile, as shown in U.S. Patent No. 2,920,- 357 and in FIG. 3.

As illustrated in FIG. 3, the foil backed tiles 10 are supported onthe ported runners 44 and similar cross members 50, with the foil back upwardly disposed. The

runners are supported by wires 46 attached to the structure, not shown, of the upper boundary of the room in which the ceiling is supported. "The entire plenum chamber is not shown but normally constitutes the enclosure defined by the suspended ceiling, the upper boundary of the room, and the lateral walls of the room'extending .between the upper boundary and the; suspended ceiling. 'Air is introducedinto the plenum chamber and passes in a well distributed and uniform rate through ports 48 in the runners 44 and ports 51 in cross members 50.

The-opening in these ports may be adjustable to. afford control of the airflow. The runners along with the cross members are modularly spaced suchas 2 ft. on centers. The cross members are attached to the primary runner by means of clips, not shown. The tiles rest upon the ledges forming the lower portion of the-runners and cross members, with the tile-edges forming the joints between adjacent tiles hot-so supported being reinforced by spline members 52 placed into the kerfs 16 of each tile. The spline members may be formed from sheet metal with a slight reinforcing ridge extending down the center. It isimportant in this type:of construction that there is a closefit between the spline members and the kerfs so as to prevent any passage of air through the joint.

' Y The ceiling construction of FIGS maintains the pleasing appearance and functional advantage arising from the At the same except through the controlled ports. The net results are more accurate distribution and control of the air flowing from the plenum chamber into the room below and the'allowance of higher pressures in the plenum chamber.

The ceiling 53 illustrated in FIG. 4 employs tile produced according to the teachings of this invention and is well suited for a sound correcting suspended ceiling construction having high resistance to fire. In this construction the tiles are joined together and supported by sheet metal flanges or splines at all the joints, whereby the passageof gases through the joints between adjacent tile is substantially eliminated. The foil backed mineral fiber tiles 10 are supported on flanged runners 54 by the lower flanges 56 engaging the kerfs extending'along the edges of adjacent tiles. .The edges of adjacent tiles not directly supported on the runners are joined by splines 52. Flanged runners 54 are attached to the channels 58 by means of clips 60. -The channels are supported by wires 62 which are attached to the structure above, not shown. Ceiling 53 extends between the walls of the room in which it is suspended and no open ports are provided in this construction. The result is a substantially impervious mineral fiber tile ceiling which prevents the passage of hot gases either through or around the tile. When properly erected, this type of construction has provided high fire rating test results. The foil stops the passage of the hot gas through the body of the tile while the use of the spline members and the flange runners prevents any passage through the joints, between adjacent tile. Thus, there is a barrier to the passage of hot gases, which contrib tes'to gh fire rating e It has been found that the use of a foil across the entire back surface of mineral fiber acoustical tile, such as set forth above, will not adversely affect the sound absorption characteristics thereof. In fact, there is an unexpected increase in the sound attenuation factor. For instance, in structures embodying this invention, attenuation factors as high as 45 decibels have been attained as compared with about 31.5 decibels without the aluminum foil.

It will thus be seen that an improved ceiling tile and an advantageous ceiling construction have been provided. A molded mineral fiber acoustical tile is disclosed in which a layer of aluminum foil extends over and is conterminous With the back surface of the tile and is made a part thereof during its manufacture by spreading the composition forming the body of the tile upon a sheet of foil applied as a liner over the bottom of a mold. The step of sanding the back surface is eliminated with consequent saving in labor and material. There are significant improvements in drying of the tile. The tile may present a porous and fissured lower surface to obtain good acoustical characteristics and pleasing appearance but are still impervious to passage of gases therethrough and are economical to produce. Utilizing such tile, a ceiling construction is provided which facilitates control and uniform distribution of air through a suspended ceiling of mineral fiber acoustical tile from a plenum formed by the ceiling and the structure thereabove. The tile provides a pleasing appearance and equal or improved acoustical properties while preventing any passage of air therethrough so that properly spaced openings to give the desired air distribution can be used without erratic and/ or extraneous flow of air through random fissures, high porosity areas, and the like, of varying degrees of air transmission. Further, in structures without intentionally formed openings, tiles produced in accordance with this invention facilitate obtaining a high fire rating.

While particular embodiments of the invention have been shown, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art in light of the fore-going teachings. It is, therefore, contemplated by the appended claims to cover any such modifications as fall within the true spirit and scope of the invention.

I claim:

1. An acoustical tile comprising a relatively thin, flat body of acoustical composition including fibrous material and an amylaceous binder, said body being porous and normally having intrinsic gas passageways therethrough, and a layer of sheet material impervious to passage of Water vapor, said layer being coextensive with the back surface of said tile and firmly bonded thereto throughout substantially the entire area of said layer by said binder.

2. An acoustical tile as in claim 1 wherein said sheet material is aluminum foil.

3. An acoustical tile as in claim 2 wherein said acoustical composition comprises a mixture of starch and mineral Wool.

4. An acoustical tile as in claim 1 wherein said tile is provided with spaced openings therethrough for passage of air.

References Cited by the Examiner UNITED STATES PATENTS 1,769,519 7/1930 King et al. 18133.11 1,950,420 3/1934 Stitt 18133.1 2,021,359 11/1935 Halstead 18133.1 2,221,001 11/1940 Lucius 18133.1 2,587,884 3/1952 Palmer 18133.1 2,717,538 9/1955 Alexander 18133.1 2,785,099 3/1957 Holtsford 18133.1 2,807,993 10/1957 Ericson 18133.1 2,890,147 6/1959 Pearson et a1 181-3311 2,920,357 1/1960 Ericson 18l33.1 2,996,765 8/1961 Nelsson 18133.1 3,122,216 2/1964 Boltz et al. 18133.1

FOREIGN PATENTS 296,295 4/ 1954 Switzerland.

RICHARD B. WILKINSON, Primary Examiner.

R. B. WARD, Assistant Examiner. 

1. AN ACOUSTICAL TILE COMPRISING A RELATIVELY THIN, FLAT BODY OF ACOUSTICAL COMPOSITION INCLUDING FIBROUS MATERIAL AND AN AMYLACEOUS BINDER, SAID BODY BEING POROUS AND NORMALLY HAVING INTRINSIC GAS PASSAGEWAYS THERETHROUGH, AND A LAYER OF SHEET MATERIAL IMPERVIOUS TO PASSAGE OF WATER VAPOR, SAID LAYER BEING COEXTENSIVE WITH THE BACK SURFACE OF SAID TILE AND FIRMLY BONDED THERETO THROUGHOUT SUBSTANTIALLY THE ENTIRE AREA OF SAID LAYER BY SAID BINDER. 